This proposal will focus on the following objectives: (1) To define the in vivo capacity of ts G41 infection in BALB/c mice to produce persistent or chronic CNS viral infection. (2) To study the neurovirulence of various clonal isolates of ts G22 and ts G31 by means of cloning brain and spinal cord isolates and testing representative plaque purified clones with respect to plaque morphology and size, growth kinetics in neuroblastoma and BHK-21 cells at 31 degrees, 37 degrees and 39 degrees C and in vivo clinical and histopathological behavior. (3) To study the behavior of wt and selected ts VSV mutants in neurally derived cell lines. Cell lines to be used include N2A, N-18 (murine neuroblastoma), C-6 rat glioma and ependymoma cells. Studies include growth kinetics and mechanisms of maturation and replication in vitro using light, transmission and scanning electron microscopy. (4) To define the in vivo subcellular localization of major VSV antigens, i.e. G, M, N proteins, in infected neurons in vivo by means of an immunoperoxidase technique. (5) To study additional ts VSV mutants belonging to complementation groups II and III. Since the slowly progressive CNS infection and spongiform myelopathy are seen with Glasgow mutants belonging only to complementation groups II and III, these studies will determine whether the production of spongiform myelopathy is a general property of certain complementation groups or unique to individual mutants. (6) To define the in vivo capacity of Chandipura virus and selected ts mutants of this human rhabdovirus to produce CNS disease. (7) To define the in vivo interaction occurring between homologous DI particles and ts VSV mutants. (8) Biochemistry: A major segment of the proposed study will involve the characterization of the growth kinetics and RNA and viral protein synthesis of the original cloned temperature-sensitive VSV mutants ts G22 and G31 that produced the prolonged CNS disease and spongiform neuropathology. As a result, a comparative biochemical study of these clonal isolates as well as the original mutants will be one of the major focuses of the proposed research. (Text Abridged.)